Hypodermic syringe with retractable needle mount

ABSTRACT

A hypodermic syringe (10) comprising a barrel (14) for containing medicament or other liquid, movable piston means (16) including a shaft (40) provided with a chamber (42) and frangible chamber sealing means (20), needle mounting means (22) disposable within barrel (14), spring means (18) for imparting movement to needle mounting means (22), and restraining means (28) in barrel (14) comprising an annular structure (36) located towards first end (30) of barrel (14) extending inwardly thereof and containing a plurality of radially-extending weakened portion (38), wherein needle mounting means (22) when in a first position extends partway from first end (30) and is restrained from movement by engagement with restraining means (28), the restraining means (28) being operable to release needle mounting means (22) when piston (16) approaches first end (30) and then to engage and restrain piston (16) from reverse movement, the needle mounting means (22) on release having been propelled through frangible diaphragm (66) to a second position wherein it is received and retained within chamber (42) in a jamming relationship.

FIELD OF THE INVENTION

This invention relates to a hypodermic syringe and more particularly toa hypodermic syringe incorporating means for retracting a needle withinthe syringe and thereby preventing re-use of the syringe.

BACKGROUND OF THE INVENTION

Presently, there is considerable concern within the general public andwithin the medical profession relating to injuries or infections causedby accidental stabbing of a person by a needle affixed to a hypodermicsyringe. Such injury or infection is commonly referred to as a"needle-stick injury". This type of injury arises because hypodermicsyringes currently in use are provided with needles which are exposedbefore and after use of the hypodermic syringe. Capping or shielding ofneedles can be employed. However, needle-stick injuries can occur duringrecapping or reshielding after the syringe has been used. For thisreason recapping is forbidden in many medical institutions.Additionally, re-use of a used syringe exposes persons to the risk ofinfection.

A number of solutions to the problems caused by exposed needles on usedsyringes have been advanced. For instance, Australian Patent ApplicationNo. 628814 discloses a hypodermic syringe having a retractable needlecarried in a needle support mounted on the end of the syringe body, theneedle being attached to a needle holder which has a conical head on theend distant from the point of the needle. A passage in the needle holderenables communication between the needle bore and the chamber of thesyringe through holes in the needle holder. The piston has a sealing capengaged therewith and also a forwardly extending tubular portiondefining an opening with a tapered wall which engages over the conicaledge of the needle holder to lock the head behind an abutment surfacewhen the piston is pushed in. At the same time a diaphragm formed by thesealing cap extending across the tubular portion of the piston isruptured so that the chamber of the syringe is no longer sealing theenclosed. Withdrawal of the piston and the associated plunger draws theneedle into the chamber. The needle can then be received into a housingwithin the body of the plunger. This approach was perceived asaddressing or overcoming disadvantages seen in the complexity ofarrangements such as those disclosed in the U.S. Pat. Nos. 4,779,655,4,710,170, 4,675,005, 4,650,468, 4,592,744 and 4,507,117.

However movement of the piston away from the closed end of the body ofthe syringe is necessary if the needle is to be drawn into the chamberof the syringe. Prior to this manoeuvre being completed the potentialfor needle-stick injury is still real. Additionally, further movementsare required to effect receival of the needle into the housing providedin the body of the plunger of the piston.

Other solutions have been proposed in International Patent ApplicationNo. PCT/ES90/00002, U.S. Pat. No. 5,049,133, U.S. Pat. No. 4,838,869,U.S. Pat. No. 4,966,593, International Application No. PCT/FR90/00656,and Australian Patent Applications 57097/90 and 39180/89. However, thesespecifications concern themselves with what are called "fixed needle"syringes. The needles on these syringes are not capable of beinginterchanged to take different requirements into account. Further, thesyringes have an appreciable number of components, leading to relativelyhigh manufacturing costs.

The present invention seeks to provide a hypodermic syringe which willbe useful in reducing needle-stick injury and which will permitinterchanging of needles to meet varying requirements.

The present invention also seeks to provide a hypodermic syringe which,after use, cannot be re-used.

The present invention also seeks to provide a hypodermic syringe whichis economical to manufacture and has a small number of components.

Other objects, advantages or features of the present invention as setforth in the following description all will become apparent by practiceof the present invention.

DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided ahypodermic syringe comprising a barrel for containing medicament orother liquid,

piston means movable within said barrel between a first end and a secondend thereof,

needle mounting means disposable within said barrel,

means for imparting movement to said needle mounting means,

restraining means located towards said first end,

said needle mounting means when in a first position having a portionthereof extending from said first end and being restrained from movementby engagement with said restraining means,

said restraining means being operable to release said needle mountingmeans when said piston means approaches said first end and then toengage and restrain from reverse movement said piston means,

said piston means having a shaft provided with a chamber capable ofreceiving and retaining said needle mounting means and frangible sealingmeans to seal said chamber,

wherein said needle mounting means, when released, is propelled fromsaid first position to a second position wherein it is received andretained within said chamber after passing through said frangiblesealing means.

Preferably said means for imparting movement is a spring undercompression. More preferably the spring is a coil spring.

The portion of the needle mounting means, or "shuttle", that extendsfrom the barrel terminates in a taper on which interchangeable needlescan be seated. Preferably the taper is an international standard taper.In use a needle, being firmly seated on the taper, consequently isconveyed into the chamber in the shaft of the piston means along withthe shuttle when the shuttle is released.

Preferably the walls of the chamber in the shaft of the piston means areso shaped as to engage the shuttle in a firm holding relationship whenthe shuttle is propelled into the chamber. More preferably thelongitudinal wall or walls of the chamber is or are so geometricallyconfigured that the shuttle is held fast in a jamming relationship afterit has been propelled into the chamber.

The restraining means is integral with the barrel and preferably takesthe form of an annular structure extending inwardly of the inner wall ofthe barrel. More preferably the annular structure contains a pluralityof radially-extending weakened portions, which are fractured by forcesexerted by means provided on the piston means. Still more preferably therestraining means engages the piston means after release of the shuttlein such a manner that the piston means cannot be withdrawn withoutcausing further damage to the restraining means.

Preferably, means are provided to prevent premature or accidentalrelease of the shuttle. Such means can take the form of a detachable lugon the shaft of the piston means capable of engaging a portion of thebarrel (preferably the second end) and thereby limiting the range ofmovement of the piston means towards said first end and preventing saidpiston means from operating said restraining means.

DESCRIPTION OF PREFERRED EMBODIMENTS

In order that the invention may be more clearly understood and readilyput into effect a preferred non-limiting embodiment is now describedwith reference to the accompanying drawings in which

FIG. 1 is a longitudinal sectional view through a preferred embodimentof the invention prior to release of the shuttle;

FIG. 2 is a longitudinal sectional view of the embodiment of FIG. 1after release of the shuttle;

FIG. 3 is a longitudinal sectional view of the barrel of the embodiment;

FIG. 4 is a cross-sectional view of the barrel along line A--A of FIG.3;

FIG. 5 is a longitudinal sectional view of the piston means of theembodiment;

FIG. 6 is a cross-sectional view of the piston means along line C--C ofFIG. 5;

FIG. 7 is a partially cut away perspective view of the frangible sealingmeans;

FIG. 8 is a spring being the movement imparting means;

FIG. 9 is a longitudinal sectional view of an end cap for the barrel;

FIG. 10 is a perspective view of the upper part of a shuttle;

FIG. 11 is a top plan view of the shuttle of FIG. 10; and

FIG. 12 is a longitudinal sectional view of the shuttle along line D--Dof FIG. 11.

In the drawings the numeral 10 generally designates a preferredhypodermic syringe and the numeral 12 generally designates a hollow boreneedle. Numeral 14 designates the barrel of the hypodermic syringe,numeral 16 designates the piston means, numeral 18 designates thespring, numeral 20 designates the sealing means, numeral 22 designatesthe shuttle, and numeral 24 designates the end cap.

The barrel 14 is a one piece moulding incorporating a finger grip 26 anda shuttle retainer 28, forming the restraining means, located close toopen first end 30. The first end is closed off by end cap 24 while theopen second end 32 receives piston means 16. The annular disc-likeshuttle retainer 28 takes the form of a truncated hollow cone the apexof which is directed towards first end 30. The centre 34 of the shuttleretainer is open and the annulus 36 is provided with a plurality ofradially-extending weakened portions 38.

The piston means 16 is also a one piece moulding comprising a shaft 40defining a chamber 42, centralising fins 44, a thumb pad 46, a snap-offlock pin 48, and trigger and locking means 50. The lower end 52 ofchamber 42 is open and can be sealed by frangible sealing means 20. Theupper end 54 of chamber 42 is closed and the wall 56 of the chamber 42adjacent upper end 54 is tapered inwardly. This is to provide a firmengagement with the shuttle 22 when it has been impelled into chamber 42on its release from the shuttle retainer 28. The centralising fins 44serve to keep the piston means 1 6 oriented correctly within barrel 14.The snap-off lock pin 48 is integral with one of the centralising fins44 and here takes the form of a radially extending tab which engages thefinger grip 26 of the barrel 14 and prevents the piston means 16 beingpushed further into the barrel 14 towards first end 30. The snap-offlock pin 48 can be readily snapped off when required. The trigger andlocking means 50 are designed so that in use annular shoulder 58 engagesupper surface 60 of shuttle retainer 28 as the piston means 16 is fullydepressed. The piston means 16 is also provided with annular depression62 to receive the O-ring 64 of frangible piston sealing means 20, thefrangible diaphragm 66 of which covers open lower end 52.

The piston sealing means 20 is a one-piece neoprene type moulding withthe frangible diaphragm 66 being of such a thickness that it provides asatisfactory seal for chamber 42 and yet can be pierced readily bypiercing means provided on the shuttle 22. The O-Ring 64 abuts the innerwall of barrel 14 in a sealing relationship.

Shuttle 22, which is a one-piece moulding, comprises a shaft 68 withbore 74 along the longitudinal axis thereof. One end of shaft 68terminates in a standard taper 70 which can receive complementary hollowneedle 12 and the other end of the shuttle is provided with spike means72 for piercing the frangible diaphragm 66. Spike means 72 comprises apart-cone partly bounding bore 74 and permits communication between thebore 74 and the inside of the barrel 14. An annular shoulder 76 isdisposed round the shuttle adjacent to the upper end. This annularshoulder 76 is engaged by the shuttle retainer 28 as is shown in FIG. 1and also prevents the shuttle retainer falling out of the syringethrough the end cap.

One-piece moulding end cap 24 is provided with a cylindrical wall 78 andannular flange 80 so sized as to permit it to be seated securely on thefirst end of barrel as is shown in FIG. 1. During assembly of thesyringe heat welding or suitable adhesives may be used to fix the endcap in place. Shoulder 82 acts as a seat for spring 18 as is shown inFIG. 1. Bore 84 is so sized as to permit inward passage of portion ofshaft 68 and needle 12 mounted on the shuttle.

The spring 18 is formed from surgical quality steel and is capable ofexerting force sufficient to drive the shuttle 22 firmly into thetapered upper portion of the chamber 42 defined by wall 56. The othercomponents may be constructed from any suitable material or combinationsof materials. As can be seen, a hypodermic syringe according to thepresent invention has a small number of components, thereby lesseningmanufacturing costs.

In use a selected needle is mounted on the taper of the shuttle and thebarrel is filled in a conventional manner by drawing out the pistonmeans. After filling is complete and the required dose is obtained, thesnap-off lock pin 48 is broken off and the injection is given. Duringthe completion of the injection stroke the following occurs in sequence:

(a) the spike means 72 on the shuttle 22 pierces the frangible diaphragm66;

(b) the lower end 52 of the piston means 16 engages the upper surface 60of the shuttle retainer 28 and fractures the annulus 36 along theplurality of radially-extending weakened portions 38;

(c) the lower end 52 of the piston means 16 spreads the "leaves" soformed, thereby disengaging them from the annular shoulder 76 of shuttle22 and permitting the shuttle 22 with needle 12 attached to be propelledinto the chamber 42 of the piston means 16 with such force that theshuttle 22 is jammed into the tapered upper portion of the chamber 42defined by wall 56 and held there;

(d) the lower end 52 of the piston means 16 passes through the "leaves"which then spring back over the top of the small annular shoulder 58 andengage it thereby restraining withdrawal of the piston means 16, asshown in FIG. 2.

The hypodermic syringe and needle cannot be reused as the shuttleretaining means has been fractured and the shuttle and needle have beencaught within the chamber in the piston means. The piston means cannotbe withdrawn without further destruction of the shuttle retaining means.

It is believed that the invention and many of its attendant advantageswill be understood from the foregoing description and it will beapparent that various changes may be made in the form, construction, andarrangement of the hypodermic syringe and the changes may be made in theform, construction and arrangement of the preferred embodiment describedwithout departing from the spirit and scope of the invention orsacrificing all of its material advantages.

We claim:
 1. A hypodermic syringe as comprising a barrel for containing medicament or other liquid, piston means movable within said barrel between a first end and a second end thereof, needle mounting means disposable within said barrel, means for imparting movement to said needle mounting means, restraining means located towards said first end, said needle mounting means when a first position having a portion thereof extending from said first end, said extending portion being provided with a taper on which an interchangeable needle can be seated, said needle mounting means being restrained from movement by engagement with said restraining means, said restraining means being integral with said barrel and taking a form of an annular structure extending inwardly of the inner wall of the barrel, said annular structure containing a plurality of radially-extending weakened portions, which may be fractured by force exerted by means provided on said piston means, and being operable to release said needle mounting means when said piston means approaches said first end and then to engage and restrain from reverse movement said piston means, said piston means having a shaft provided with a chamber capable of receiving and retaining said needle mounting means and frangible sealing means to seal said chamber, wherein said needle mounting means, when released, is propelled from said first position to a second position wherein it is received and retained within said chamber after passing through said frangible sealing means, wherein said annular structure contains a plurality of radially-extending weakened portions, which may be fractured by forces exerted by means provided on said piston means.
 2. A hypodermic syringe as claimed in claim 1 wherein said restraining means engages said piston means after release of said needle mounting means so that said piston means cannot be withdrawn from said first end of the hypodermic syringe without causing damage to said restraining means.
 3. A hypodermic syringe as claimed in claim 1 wherein said restraining means engaged said piston means after release of said needle mounting means so that said piston means cannot be withdrawn from said first end of the hypodermic syringe without causing damage to said restraining means.
 4. A hypodermic syringe as claimed in claim 1 wherein said means for imparting movement is a spring under compression.
 5. A hypodermic syringe as claimed in claim 1 wherein the walls of said chamber are so shaped as to engage said needle mounting means in a firm holding relationship when said needle mounting means has been propelled into said chamber.
 6. A hypodermic syringe as claimed in claim 5 wherein said firm holding relationship is a jamming relationship.
 7. A hypodermic syringe as claimed in claim 1 wherein means are provided to prevent premature or accidental release of said needle mounting means.
 8. A hypodermic syringe as claimed in claim 7 wherein said means to prevent premature or accidental release comprise a detachable lug provided on the shaft of the piston means, said detachable lug being capable of engaging of the second end of said barrel and thereby limiting the range of movement of the piston means towards said first end.
 9. A hypodermic syringe comprising a barrel for containing medicament or other liquid, piston means movable within said barrel between a first end and a second end thereof, needle mounting means disposable within said barrel, means for imparting movement to said need mounting means, restraining means located towards said first end, said needle mounting means when in a first position having a portion thereof extending from said first end, said extending portion being provided with a taper on which an interchangeable needle can be seated, said needle mounting means being restrained from movement by engagement with said restraining means, said restraining means being integral with said barrel and taking a form of an annular structure extending inwardly of the inner wall of the barrel, said annular structure containing a plurality of radially-extending weakened portions, which may be fractured by forces exerted by means provided on said piston means, and being operable to release said needle mounting means when said piston means approaches said first end and then to engage and restrain from reverse movement said piston means, said piston means having a shaft provided with a chamber capable of receiving and retaining said needle mounting means and frangible sealing means to seal said chamber, wherein said needle mounting means, when released, is propelled from said first position to a second position wherein it is received and retained within said chamber after passing through said frangible sealing means; wherein said restraining means engages said piston means after release of said needle mounting means so that said piston means cannot be withdrawn from said first end of the hypodermic syringe without causing damage to said restraining means.
 10. A hypodermic syringe as claimed in claim 9 wherein said means for imparting movement is a spring under compression.
 11. A hypodermic syringe as claim in claim 9 wherein the walls of said chamber are so shaped as to engage said needle mounting means in a firm holding relationship when said needle mounting means has been propelled into said chamber.
 12. A hypodermic syringe as claimed in claim 11 wherein said firm holding relationship is a jamming relationship.
 13. A hypodermic syringe as claimed in claim 9 wherein means are provided to prevent premature or accidental release of said needle mounting means.
 14. A hypodermic syringe as claimed in claim 13 wherein said means to prevent premature or accidental release comprise a detachable lug provided on the shaft of the piston means, said detachable lug being capable of engaging of the second end of said barrel and thereby limiting the range of movement of the piston means towards said first end. 